1. Technical Field
The present invention relates to an adjustable tension cuff assembly for use with a medical device, such as a device for monitoring the flow of a bodily fluid through a body vessel.
2. Background Information
A variety of microsurgical procedures have been developed in recent years which have saved the lives of patients, and/or significantly improved the quality of life for patients. Such procedures include organ transfer surgery, reconstructive surgery following the removal of tumors (particularly in the areas of the head and neck), coronary artery bypass grafting (CABG) procedures, and reconstructive surgery such as free tissue transfer and the like. Free tissue transfer typically entails the removal of tissue and/or muscle from one part of the body, along with an associated artery and vein, and the reattachment of the tissue and/or muscle to another part of the body. The artery and vein of the transferred tissue and/or muscle are then anastomosed (that is, connected) to a native artery and vein in order to achieve blood circulation in the transferred tissue and/or muscle.
The success of such transfer or reconstruction lies in obtaining good patency of the anastomosis, and hence, good patency in the transferred tissue and/or muscle (sometimes referred to as the flap). A primary complication in microvascular surgery such as free tissue transfer is thrombosis. Unrecognized thrombosis reduces patency in the flap and reduces the probability of salvaging the flap. The window of opportunity for salvage after thrombosis is presently believed to be only about six hours of warm ischemia. It is therefore critical that any vascular thrombosis in a transferred flap be recognized and any resulting ischemia be remedied as soon as possible. While the success rate of the free tissue transfer procedure is generally quite favorable, it is desired to improve the success rate to an even greater degree. Even though failure rates are generally low, any surgical failure can be costly, both to the patient and the medical provider. It would be highly desirable to reduce the failure rate of this and similar techniques.
A variety of operative and post-operative monitoring techniques are presently used for clinically assessing thrombosis and identifying the resulting ischemia. One widely-used technique utilizes an implantable ultrasonic Doppler probe that is positioned directly on the anastomosed vein and/or the artery. Such a probe includes an implanted piezoelectric transducer carried on a cuff or sleeve that is wrapped around the blood vessel of interest. The transducer is used to alternately generate ultrasonic waves and measure backscattering of those waves. Since blood is a very effective backscattering medium, the Doppler shift in the frequency of the backscattered ultrasonic waves yields a precise and accurate measurement of the blood velocity and, by implication from the cross-sectioned area of the blood vessel, the volume of blood flow in the vessel of interest. Monitoring of blood flow in this manner normally provides effective early warning of thrombosis, thereby significantly increasing the chances of salvaging the flap.
In this technique, the cuff is snugly arranged around the vessel, and the respective ends of the cuff are joined by sutures or by a clip. This manner of attachment has certain drawbacks. For example, if an inadequate signal is attained, it is often necessary to remove the clip or sutures, and reposition the cuff and transducer in a manner such that a stronger signal is received. In this event, the clip or sutures must be removed, the cuff must be rearranged, and the clip or sutures must then be reattached at the new position. In addition, there are numerous possible vessels in the body of the patient that may be subject to monitoring for fluid flow. Although it would be desirable to have a separate cuff available to fit each size vessel, this is often not possible in actual practice. As a result, for example, it may be necessary to wrap a large cuff around a small vessel. In this event, the large diameter of the cuff may make it cumbersome to work with, and may obstruct at least a portion of the signal from the transducer.
Another drawback to the use of the conventional cuffing arrangement occurs when such cuffs are used with pediatric patients. With pediatric patients, the vessel of interest may continue to grow subsequent to installation of the cuff. In this event, a cuff whose ends are secured by a clip or by sutures may undesirably restrain the vessel from expanding. While a cuff may be secured using a clip or sutures fabricated from bio-absorbable/dissolvable material, the cuff may later migrate and erode through the patient's skin. Yet another drawback with such conventional cuffs is that the tension of the cuff on the patient's vessel may not be known until the cuff has been secured on the vessel. If it is determined that the cuff is too tight, or too loose, then the clip or sutures must be removed, and the cuff must generally be replaced with a new cuff.
Other known devices and techniques have their own drawbacks. Accordingly, it would be highly desirable to provide a cuff assembly for use in a medical device, such as a device for monitoring fluid flow through a vessel during or after a surgical procedure, wherein the cuff assembly can be easily and quickly attached to a body vessel, and can be easily and quickly removed, realigned and/or reattached if necessary. It would also be highly desirable to make such an assembly suitable for use with vessels of varying sizes. In addition, it would be highly desirable that the assembly be susceptible of re-adjustment if it is determined that the initial placement attained when the assembly is wrapped around the vessel is inadequate, or when a suitable initial placement or tension later becomes unsuitable due to a change in conditions, such as the growth of the vessel.